Degenerative joint disease, the clinical name for osteoarthritis, happens when the cartilage cushioning your joints breaks down faster than your body can repair it. Over 595 million people worldwide have the condition, and roughly 30% of adults over 55 are living with it. The causes range from simple wear over decades to specific injuries, excess body weight, and metabolic changes that quietly damage joint tissue from the inside.
How Cartilage Breaks Down
Healthy cartilage constantly rebuilds itself. Specialized cells called chondrocytes produce new structural proteins (collagen and proteoglycans) while enzymes clear away old, damaged material. In a healthy joint, production and cleanup stay roughly balanced.
In degenerative joint disease, that balance tips toward destruction. The enzymes responsible for breaking down cartilage, known as matrix metalloproteinases, become overactive. They chew through collagen and proteoglycans faster than chondrocytes can replace them. Early on, your body tries to compensate: chondrocytes multiply and ramp up production of new cartilage material. But as the disease progresses, the repair effort can’t keep pace with the damage.
What makes this worse is a built-in feedback loop. Some of these destructive enzymes can activate other dormant enzymes, creating a chain reaction that accelerates cartilage loss. Inflammatory signaling molecules, particularly one called interleukin-1, push chondrocytes and the cells lining the joint to produce even more of these enzymes. The result is a self-reinforcing cycle of inflammation and tissue breakdown that, once established, is difficult to reverse.
Aging and Cell Burnout
Age is the single strongest risk factor. As you get older, chondrocytes accumulate damage and eventually enter a state of senescence, meaning they stop dividing and functioning normally. Instead of quietly retiring, these worn-out cells start pumping out inflammatory molecules and tissue-degrading enzymes. This pattern acts as a bridge between normal aging and the chronic inflammation that drives joint degeneration. It helps explain why osteoarthritis is so much more common after middle age, even in joints that were never injured.
How Excess Weight Damages Joints
Carrying extra body weight stresses weight-bearing joints like the knees and hips, but the damage goes well beyond mechanical pressure. Fat tissue is metabolically active. As it accumulates, it releases signaling molecules that travel through the bloodstream and reach joint tissue. One of the most studied is leptin, a hormone produced predominantly by white fat cells.
Leptin has a strong synergistic relationship with inflammatory compounds in osteoarthritis. In cartilage, it ramps up the production of several inflammatory mediators and directly triggers the release of the same destructive enzymes that break down cartilage. Elevated leptin also impairs chondrocyte function, essentially making the cells responsible for cartilage repair less effective at their job. Another molecule released by fat tissue, resistin, suppresses the production of key cartilage building blocks while simultaneously increasing enzyme activity that destroys existing cartilage.
This is why osteoarthritis in people with obesity often affects non-weight-bearing joints like the hands. The inflammatory signals from fat tissue circulate systemically, reaching joints that aren’t under any extra mechanical load. Abnormal dietary factors like excess lipids and glucose further compound the problem by triggering additional inflammatory mediators throughout the body.
Joint Injuries and Post-Traumatic Arthritis
About 12% of the overall burden of osteoarthritis traces back to a prior joint injury. Torn ligaments, meniscus damage, and fractures that extend into a joint surface all significantly raise the risk. What surprises many people is the timeline: osteoarthritis can develop within as few as 2 years after a severe joint fracture, though less serious injuries may take decades to cause noticeable degeneration.
Post-traumatic osteoarthritis also tends to strike much younger. Patients typically develop it between ages 18 and 44, far earlier than the age-related form of the disease. An ACL tear in your twenties, for instance, can set the stage for knee arthritis by your thirties or forties. The initial injury disrupts the joint’s mechanical alignment, changes how forces distribute across the cartilage surface, and triggers inflammatory processes that may smolder for years before symptoms appear.
Occupational and Repetitive Stress
Certain jobs carry a measurably higher risk. Heavy physical workloads are the most consistently identified occupational risk factor, and the effect shows up across multiple joint sites. Specific activities linked to accelerated joint degeneration include frequent kneeling, regular stair climbing, crawling, bending, exposure to whole-body vibration (common in truck drivers and heavy equipment operators), and repetitive motions. Construction workers, farmers, floor layers, and miners appear in the research repeatedly as high-risk groups. The common thread is sustained, repetitive mechanical loading of the same joints over years or decades.
Primary vs. Secondary Causes
Doctors sometimes classify osteoarthritis as primary or secondary. Primary osteoarthritis has no single identifiable trigger. It develops gradually from the combined effects of aging, genetics, and the cumulative mechanical stress of daily life. This is the most common form and the one most people think of when they hear “wear and tear.”
Secondary osteoarthritis has a clear underlying cause. This includes prior joint injuries, congenital joint deformities that alter alignment from birth, infections that damage cartilage, and metabolic conditions. The distinction matters because secondary forms can sometimes be slowed or prevented by addressing the root cause early, whether that means surgical repair of a joint injury, correcting alignment problems, or managing metabolic health.
The Role of Genetics
Family history plays a real role, particularly for osteoarthritis of the hands and hips. Studies on twins and families estimate that genetic factors account for 40% to 65% of the variation in who develops the disease. No single gene is responsible. Instead, multiple genes influence cartilage structure, inflammatory responses, and how efficiently your body repairs joint tissue. If your parents or siblings developed osteoarthritis relatively early, your own risk is elevated.
What Happens Inside the Joint Over Time
Cartilage loss is the hallmark, but it’s not the whole picture. As cartilage thins, the bone underneath responds by becoming denser and forming small bony growths (bone spurs) around the joint margins. The synovial membrane lining the joint often becomes inflamed, producing excess fluid that causes swelling. Ligaments and tendons around the joint can weaken or tighten, altering mechanics further. In advanced stages, cartilage may wear away entirely in spots, leaving bone grinding against bone.
This cascade explains why degenerative joint disease involves more than just cartilage. It’s a whole-joint process, and by the time pain becomes persistent, multiple tissues are usually involved. The inflammatory signals driving cartilage loss also affect bone remodeling, synovial tissue, and the surrounding soft structures, which is why treatment approaches that target only one element rarely halt progression entirely.